The present invention relates to an image stabilizing apparatus that corrects an image shake due to, for example, a hand shake to prevent degradation of a picked-up image, and an optical apparatus having the image stabilizing apparatus.
In current cameras, all important tasks for image pickup such as exposure decisions, focusing and the like are automated, so that even amateurs in camera operation are much less likely to fail in image pickup.
Recently, cameras provided with a system for preventing an image shake due to a hand shake have also been put on the market, virtually eliminating any factors that cause a photographer to fail in image pickup.
An apparatus for correcting image shakes, also referred to as image stabilizing apparatus, will now be briefly described.
A hand shake on a camera in image pickup is typically a shake from 1 Hz to 10 Hz in terms of a frequency.
In order to ensure that the camera can pick up an image without an image shake even if such a hand shake occurs when the shutter is released, the shake of the camera due to the hand shake must be detected and an image correction lens must be moved depending on the detected value.
Therefore, in order to pick up an image without the image shake even if a camera shake occurs, firstly the shake of the camera must be accurately detected, and secondly, the variation of the optical axis due to the hand shake must be corrected.
The detection of the shake (or camera shake) can be accomplished with a shake detector mounted on the camera. Fundamentally, the detector detects the acceleration, angular acceleration, angular velocity, angular displacement and the like, and appropriately computes the output for camera shake correction.
Based on the detection information, the image stabilizing apparatus that decenters the image pickup optical axis is driven to correct the image shake.
FIG. 10A shows a plan view of a conventional single-lens reflex camera, and FIG. 10B shows a side view of the same.
An image stabilizing system mounted on an interchangeable lens 90 that constitutes a part of the single-lens reflex camera system corrects an image due to camera shakes in the pitch and yaw directions indicated by arrows 92p and 92y, respectively, relative to an optical axis 91.
Incidentally, reference character 93a denotes a release member (or release button), 93b denotes a mode dial (including a main switch), 93c denotes a retractable flash, and 93d denotes a camera CPU provided in a camera body 93.
In FIGS. 10A and 10B, reference character 94 denotes an image pickup element, and 95 denotes an image stabilizing mechanism (or image stabilizer) that drives a correction lens 95a in the directions of arrows 95p and 95y in FIG. 10 to correct the shakes in the directions of arrows 92p and 92y. Reference characters 96p and 96y denote angular velocity meters that detect the shakes in the directions of arrows 92p and 92y, respectively. Arrows 96pa and 96ya indicate the respective sensitivity directions.
The output signals from the angular velocity meters 96p and 96y are input to a lens CPU 97 and converted thereby to a shake correction target value for the image stabilizing mechanism.
In synchronism with a half-press operation (which is hereinafter referred to as S1 and an operation that instructs the camera to perform photometering and focusing for the preparation of image pickup) of the release member 93a provided on the camera body 93, the shake correction target value is input to a coil in the image stabilizing mechanism through an image stabilizing driver 98 to start the shake correction.
The image stabilizing system illustrated in FIG. 10 uses the angular velocity meters 96p and 96y to detect hand shakes.
The camera body 93 is subjected not only to rotational shakes in the directions of arrows 92p and 92y but also to translational shakes indicated by arrows 11yb and 11pb. However, under a typical image pickup condition, the rotational shakes in the directions of arrows 92p and 92y are dominant, and the translational shakes indicated by arrows 11yb and 11pb cause less degradation of images.
Therefore, it is sufficient to provide only angular velocity meters 96p and 96y to detect hand shakes.
However, the degradation of images due to the translational shakes (hereinafter referred to as shift shakes) indicated by arrows 11yb and 11pb can not be ignored in close-up image pickup (or under an image pickup condition with large image pickup magnification).
For example, under a condition, such as macro image pickup, in which an image is picked up near a subject in the range on the order of 20 cm, or when the image pickup optical system has a very large focal length (for example, 400 mm) although the subject is located in the range on the order of 1 m, it is necessary to actively detect the shift shakes to drive the image stabilizing apparatus.
In Japanese Patent Laid-Open No. H07-225405, there has been disclosed a technique in which an accelerometer for detecting the acceleration is provided, and the shift shake is detected by the accelerometer to drive an image stabilizing apparatus along with an output from an angular velocity meter provided otherwise.
In the technique disclosed in the Japanese Patent Laid-Open No. H07-225405, the lens CPU converts the angular velocity meter output into an angle through a single integration, and converts the accelerometer output into a displacement through a double integration.
The integration operations suffer from the accumulation of slight errors in input signals, and the errors may significantly grow in the case of the double integration.
Therefore, an accelerometer that needs a double integration is required to be highly accurate.
However, there is a problem that such a highly accurate accelerometer is typically large and heavyweight and is not suitable for use in a consumer product.